The present invention relates generally to a backup and recovery system for a storage system, more particularly the present invention relates to a backup and recovery system and method for a storage system that avoids journal overflow.
Several methods are conventionally used to prevent the loss of data. Typically, data is backed up in a periodic manner (e.g. once a day) by a system administrator. Many systems are commercially available which provide backup and recovery of data; e.g., Veritas NetBackup, Legato/Networker, and so on. Another technique is known as volume shadowing. This technique produces a mirror image of data onto a secondary storage system as it is being written to the primary storage system.
Journaling is a backup and restore technique commonly used in database systems. An image of the data to be backed up is taken. Then, as changes are made to the data, a journal of the changes is maintained. Recovery of data is accomplished by applying the journal to an appropriate image to recover data at any point in time. Typical database systems, such as Oracle, can perform journaling.
Except for database systems, however, there are no ways to recover data at any point in time. Even for database systems, applying a journal takes time since the procedure includes:
1) Reading the journal data from storage (e.g., disk),
2) Analyzing the journal to determine where in the journal the desired data can be found, and
3) Applying the journal data to a suitable image of the data to reproduce the activities performed on the data, this usually involves accessing the image, and writing out data as the journal is applied.
Recovering data at any point in time addresses the following types of administrative requirements. For example, a typical request might be, “I deleted a file by mistake at around 10:00 am yesterday. I have to recover the file just before it was deleted.”
If the data is not in a database system, this kind of request cannot be conveniently, if at all, serviced. A need therefore exists for processing data in a manner that facilitates recovery of lost data. A need exists for being able to provide data processing that facilitates data recovery in user environments other than in a database application.
In a backup and recovery system using storage based journaling, the storage system must store a large number of journal entries from the processing of numerous write requests. Accordingly, the storage system requires a very large capacity in order to store the large number of journal entries. However, disks, tapes or any other such storage media have an upper limit in capacity. Thus, the storage system can not store a large number of journal entries if the capacity for storing journal entries decrease. Therefore, a need exists for a storage system that avoids journal overflow.